In typical electronic circuits, the IC circuit is designed to operate from a specific supply voltage, which is generally assumed to be constant. It is well known that a voltage regulator is used in such circuits to provide a constant DC output voltage. The voltage regulator includes circuitry that accounts for changes in load current or input voltage and adjusts such that the output voltage remains stable. For example, a feedback loop is provided wherein sensing of the output voltage is performed to allow for adjusting the output voltage to maintain same at a desired voltage.
U.S. Pat. No. 5,559,423 discloses a voltage regulator circuit including a linear transconductance amplifier with a field effect transistor (FET) as a regulating device. However, in the case where a bias feed to 2 or more GaAs PAs is required such as for a WLAN or WiMAX application where any one of PAs might be energized by the application of bias at any one time, a voltage regulator circuit with 2 or more output ports is required.
In U.S. patent Ser. No. 10/377,781 Liu et al. discloses a dual-output linear voltage regulator circuit using two voltage regulator units and a total of 3 MOSFETs to provide two terminal regulated voltages, where the second voltage is half of the first voltage. Unfortunately since the MOSFETS require significant semiconductor die area within the integrated circuit, the approach is disadvantageous as it uses 3 MOSFETs.
A need therefore exists for a compact voltage regulator with two or more switched outputs that offers a reduction in silicon die area compared to Prior Art circuits including those that employ two separate regulators or one regulator and 2 CMOS switches to provide dual output ports.